132 BERTRAM G. SMITH 



accompany the egg in its escape from the ovary; the process of 

 ovulation involves the rupture of the follicle which remains in the 

 ovary. 



The occurrence of the first polar spindle was studied in two 

 females, (A) and (B), in which the eggs were distributed from 

 ovary to uterus inclusive. The first polar spindle was found in 

 eggs taken from the following situations: ovary, body cavity, 

 oviduct, and extreme upper part of the uterus; out of a total of 

 twenty-eight eggs studied, the first polar spindle was found in 

 thirteen cases. Five eggs taken from the lower uterus were studied ; 

 no first polar spindle was found. 



In the case of another female (C), in which the eggs were all in 

 the uteri, no first polar spindle was found in three eggs sectioned. 



Allowance miist be made for the fact that in some cases in which 

 the first polar body is absent it may have been missed on account 

 of imperfections in the series. The results are sufficient to jus- 

 tify the conclusion that the first polar spindle is usually present 

 at the time the egg leaves the ovary and during its passage down 

 the oviduct, and that it disappears about the time the egg reaches 

 the uterus. 



The first polar spindle (see figs.' 32 to 35) is formed with its long 

 axis either coinciding with the axis of polarity of the egg, or oblique 

 to this axis. The number of chromosomes is probably twelve 

 before any of them have divided. There is an outer ring of six 

 large chromosomes, surrounding a central group of six small chro- 

 mosomes usually found in a state of division; it is probable that 

 these six small chromosomes are not all of equal size. These 

 size differences of the chromosomes are interesting in the light of 

 well-known recent work indicating individual differences in the 

 chromosomes of many forms. 



There is frequently present close to the cell wall overlying the 

 spindle a disc-shaped body with an irregular cross-striated struc- 

 ture, which, from its probable mode of origin, I shall call the 'con- 

 tact disc' (see figs. 33 and 34). This disc takes the cytoplasmic 

 stain, and seems to be of the same composition as the cell wall. 

 The adjacent cell wall is slightly thickened and sometimes shows 

 a cross-striation, reminding one of the zona radiata (compare the 



